Motorhome HVAC system

ABSTRACT

A unitized heating, ventilation, and air conditioning (HVAC) system for ventilating and regulating the air temperature inside a motorhome. Air is drawn from inside the motorhome and is directed to a furnace and an air conditioning unit via a common air return. A filter is positioned within the common return. The HVAC unit is compact and adapted for placement below the living area of motorhome so as to reduce the noise inside the cabin generated by the HVAC system and to reduce the center of mass of the motorhome so equipped.

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.09/971,779 entitled “Motorhome HVAC System” filed Oct. 4, 2001 which isa continuation-in-part of U.S. application Ser. No. 09/728,946 entitled“Motorhome With Increased Interior Height” filed Dec. 1, 2000. Thisapplication also claims the benefit of U.S. Provisional Application No.60/318,136 (attorney docket ALFALE.045PR) filed Sep. 7, 2001 entitled“Motorhome HVAC System.”

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to the field of vehicle heating, venting, and airconditioning (HVAC) systems and, in particular, to an HVAC systemadapted for motorhomes in which the HVAC system is substantiallypositioned outside the living portion of the motorhome and employs acommon air return system.

2. Description of the Related Art

Motorhomes have become an increasingly popular and common means ofrecreation. Motorhomes are self-propelled vehicles that include a livingspace inside. Motorhomes typically provide sleeping areas, cookingfacilities, and self-contained water supplies and toilet facilities.More elaborate motorhomes can include refrigerator/freezer units,showers and/or bathtubs, air conditioning, heaters, built in generatorsand/or power inverters, televisions, VCRs, and clothes washers anddryers. Motorhomes provide many of the amenities of a residential homewhile on the road away from home and are popular for this reason.Motorhome users will typically use the motorhome to travel to arecreational area and live in the motorhome for some period of time. Itis not unusual for people, particularly retired persons, to use amotorhome as their primary residence. Motorhome users often havefamilies with children and, as their trips are often of a recreationalnature, will often invite friends or family along on the trip.

It can be understood that since a motorhome will often be used by alarge number of people and often for an extended period of time, themotorhome manufacturers and customers will seek as many amenities and asmuch interior living space as possible. A major goal of motorhomemanufacturers and their customers is to maximize the amount of usableliving space inside their motorhomes. However, the overall size of anmotorhome is limited both by vehicle code regulations and by practicallimitations on what is reasonable to drive and maneuver. Vehicle codesrestrict the maximum height, width, and length of vehicles that may bedriven on public roads. Also, as a vehicle increases in size, it becomesincreasingly difficult to drive and can become physically too large topass through locations that the driver may wish to go. In addition, asthe motorhome gets physically larger, more fuel is required to move it,which increases the cost of operation.

An additional design constraint on the construction and design ofmotorhomes is their overall weight. Since an motorhome is intended to bemobile, an integral power plant is provided and the engine anddrive-train have an upper design limit on the weight each is capable ofmoving. In addition, the chassis, suspension, wheels, and brakes of amotorhome also have upper design limits as to how much weight they cansafely accommodate. These weight limits are established after carefulengineering analysis and the weight ratings are endorsed and enforced byresponsible governmental agencies. Exceeding the established weightlimits of a power-train or chassis component can lead to excessive wearand failure, unacceptable performance, and exposure to liability in caseof an accident. It is also highly desirable that as much payload aspossible is available to accommodate passengers and cargo, i.e.available weight load between the wet weight of the motorhome and thetotal maximum gross weight of the motorhome.

A particular issue with the weight of a motorhome is its distributionalong a vertical axis. The distance of a vehicle's center of mass fromthe road surface has a dramatic effect on the handling characteristicsof the vehicle. The closer the center of mass is to the road surface,the shorter the moment arm between the center of mass and the roll axisof the vehicle. The shorter the moment arm between the center of massand the roll axis of the vehicle, the less tendency the vehicle willhave to lean in turns. Leaning in turns is uncomfortable for theoccupants and typically places uneven loads on the tires andsuspensions, compromising turning ability. Motorhomes, typically beingquite tall, often exhibit significant leaning in turns. To minimize thisleaning, within the height available in a motorhome, the weight shouldbe concentrated as low as possible. For this reason, heavy items, suchas generators, storage and holding tanks for water and fuel, and theengine are optimally placed low in the chassis.

Since motorhomes are mobile structures, they are typically exposed tothe stresses of driving over roads that are in places quite rough. Inaddition, an motorhome will often have to travel over some distance ofdirt surface to reach a camping space. Since an motorhome is typicallyused outdoors, it is exposed to the stresses of inclement weather andhigh winds. It can be appreciated that structural integrity is highlydesired in an motorhome. However, the weight and size limitationspreviously mentioned place a limit on the strength of an motorhome.Accordingly, motorhomes are constructed to be as strong, but as light aspossible.

The chassis of a motorhome is typically constructed on a steel ladderframe chassis. The chassis is a partially complete vehicle and isgenerally procured from a manufacturer such as Freightliner or FordMotor Company. The chassis typically consists of two parallel framerails extending the length of the chassis and interconnected withseveral perpendicular cross-braces to form a ladder frame. An engine,transmission, and fuel tank(s) are generally placed between the framerails near one end. Suspension, steering, brake, and road wheelassemblies are attached outboard of the frame rails.

The coach bodywork, which provides and encloses the living space of themotorhome, is typically made from a laminate that can include lightgauge sheet metal, plywood, vinyl, and insulation. The laminate is builtto be strong, lightweight, weather resistant, and durable. The coachbodywork may also include a supporting framework. The floor of the coachtypically rests indirectly on the chassis frame and the vertical wallsextend upwards from the floor. The roof of the coach rests on anddepends on the vertical walls of the body for structural support.

A completed motorhome may be up to 45′ long and 13′6″ high in moststates. The chassis is generally on the order of 1′ high and is elevatedsome distance above the ground by the suspension and wheels to provideground clearance for suspension movement and clearing obstacles in theroad. The interior flooring in current art motorhomes is typicallyelevated a significant amount above the upper face of the chassis inorder to facilitate installing ancillary equipment. In addition, manyprior art motorhomes route cooling or heating air ducts adjacent theroof structure or mount air-conditioning units on the roof. Under theoverall height limit previously mentioned, these structures in or on theroof intrude into the available interior height envelope and limit theusable interior vertical space.

It is sometimes the practice in the art to place major components of anHVAC system, particularly air-conditioning (A/C) condensers andcompressors, on the roof of the motorhome. Placement of these A/Ccomponents on the roof does not take up limited and valuable interiorspace inside the coach. Placement of these A/C components on the roofalso exposes the condenser to fresh air which increases the efficiencyof the heat transfer performed by the A/C system.

Placement of A/C systems and/or associated ducting in the roof doeshowever create a difficulty with water condensation. As air conditioningunits cool air to a temperature below the ambient temperature, it isunderstood that in many conditions the temperature of the airconditioning unit and ducting carrying the cooled air will be below theambient dew point and thus liquid water will condense on the coolsurfaces. If these cool surfaces are located above living areas of themotorhome, as is the case with many current designs, the liquid watercan be readily drawn by gravity into the interior of the motorhome. Itwill be appreciated that liquid water intruding into the interior of themotorhome is an annoyance at best and can damage the structuralintegrity of interior structures as well as staining or warping interiorfinishings. Liquid water can also irreparably damage electronicequipment, such as laptop computers, televisions, and VCRs, such aswould often be located in the interior of a motorhome. Therefore thecondensed water is typically routed to run off the exterior surface ofthe RV. However this external draining tends to leave unsightly stainsand can drip on persons underneath.

In an A/C system the evaporator is that portion of the system thatabsorbs heat from the ambient air thereby cooling the air and providingthe air-conditioning effect. The evaporator portion of A/C system isthus preferably placed in proximity to the space to be air conditionedand the condenser and compressor portions can be readily placedelsewhere and joined to the evaporator by fluid lines. A heater orfurnace in contrast does not typically comprise separate components thatcan be readily separated. Thus, the heater or furnace portion of atypical HVAC system is a unitized assembly, separate from the A/C systemthat is preferably also placed in the space to be heated, i.e. theinterior of the motorhome coach. Disadvantageously, the combustion offuels such as propane to heat air and the operation of fans to driveheated air into the interior of the coach tends to be noisy. Thus,placement of the furnace inside the coach, while better for heatingefficiency, creates an annoyance for the occupants due to the noise ofoperation.

A further drawback to conventional HVAC systems known for motorhomes isthat they have separate A/C and heating units with separate air ductingand filtering systems. Air is routed through the air conditioning unitthrough ducting and filtering members that are completely separate fromthe heating unit's ducting and filtering members. This ductingduplication results in additional separate heating and air-conditioningair filters that require periodic changing as well as additionalinterior space consumed by the ducting. As previously mentioned,interior space within the coach is highly valuable and preferablymaximized for the occupants comfort and utility.

From the foregoing, it can be appreciated that there is a continuingneed for a stronger motorhome coach construction that also providesincreased interior living space. The structure should minimize weight tothe motorhome and should also maintain as low a center of gravity aspossible to benefit vehicle handling characteristics. There is also aneed for a HVAC system that positions noisy components outside theinterior of the coach and minimizes redundancies in ducting and filtersto reduce costs and increase interior space and serviceability. The HVACsystem preferably position the A/C condenser and ducting in such a waythat water that condenses out during use does not intrude into theinterior of the motorhome.

SUMMARY OF THE INVENTION

The aforementioned needs are satisfied by the present invention, whichin one aspect is a

As stated, the heating component is positioned outside of the interiorof the motorhome. It is understood that the heating component will makenoise during operation, and that noise could potentially annoy occupantsof the motorhome. By positioning the heating component on the outside ofthe motorhome, sound must travel through the coach body in order toreach the interior of the motorhome and any occupants therein. However,the coach body will have natural sound dampening characteristics, andadditional sound insulation might be included inside the walls of thecoach body, both of which will substantially dampen noise generated bythe heating component. Therefore, positioning the heating component assuch will significantly reduce the amount of heating component noisereaching the interior of the motorhome. These and other objects andadvantages of the present invention will become more fully apparent fromthe following description taken in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a preassembled vehicle frame mounted ona preassembled chassis forming the framework for a motorhome with a highinterior ceiling including an HVAC system with common air return;

FIG. 2 is a perspective view of an assembled heating, ventilation, andair-conditioning (HVAC) system; and

FIG. 3 is a side, section schematic view of a motorhome provided withthe HVAC system of FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Reference will now be made to the drawings wherein like numerals referto like parts throughout. FIG. 1 shows an preassembled vehicle frame 100mounted to a preassembled chassis 102. The vehicle frame 100, mounted tothe chassis 102 in the manner that will be described in greater detailbelow, facilitates the construction of a motorhome 104 (FIG. 3) with agreater interior ceiling height, which in this embodiment, is at least7′-6″ in a reduced time span. The vehicle frame 100 also facilitatesmounting of relatively massive items, such as generators, furnaces,storage and holding tanks, and the like low to the ground so as toprovide a lower center of mass for the motorhome 104.

The vehicle frame 100 provides a strong three dimensional space frame118 to inhibit twisting of the vehicle frame 100 under torsional forcessuch as would arise when the motorhome 104 drives over uneven terrain soas to lift or drop a wheel 116 with respect to the other wheels 116. Thevehicle frame 100 further defines integral storage areas 106 as part ofthe structure of the vehicle frame 100 in a manner that will bedescribed in greater detail below. As shown in FIG. 1, the storage areas106 are positioned below the beltline of the frame 100 and chassis 102.Placement of the storage areas 106 low within the motorhome 104 alsopositions items that may be stored in the storage areas 106 low withinthe motorhome 104. This aspect of the invention advantageously positionsheavy cargo that users may place in the motorhome 104 low along thevertical extent of the motorhome 104 thereby maintaining anadvantageously low center of mass.

The vehicle frame 100 further facilitates routing of a heating,ventilation, and air conditioning (HVAC) system 110 below the beltlineof the frame 100 so as to avoid intrusion of the HVAC system 110 intothe interior living space of the motorhome 104 to further enableincreased interior ceiling height of the motorhome 104 employing thevehicle frame 100. The HVAC system 110 comprises a furnace 164 and airconditioning unit 162 including evaporator, condenser, and compressor.These relatively heavy portions of the HVAC system 110 are installedbelow the beltline of the frame 100 thereby maintaining a lower c.g.than other designs.

The chassis 102 also comprises a plurality of road wheels 116 withcorresponding suspension, brake systems, steering, and drive mechanismsof types known in the art that are positioned at substantially the frontand rear comers of the chassis 102 in the manner illustrated in FIG. 1.The road wheels 116 enable the motorhome 104 to roll along the road andto be steered and braked in a well understood manner. The road wheels116 are positioned adjacent the overlapping raised rails 112 and lowerrails 114. The chassis 102 further comprises an engine assembly,transmission, drive axle, fuel system, and electrical system (notillustrated) of types known in the art to provide the motive power forthe motorhome 104. These items are advantageously located substantiallywithin the plane of the rails 112 to lower the center of mass of thechassis 102 and thus the motorhome 104.

The chassis 102 of this embodiment is highly resistant to bending alonglongitudinal and transverse axes. However, the chassis 102, by itself,is susceptible to twisting along the plane of the longitudinal andtransverse axes due to torsional forces. Such torsional force may arisewhen a road wheel(s) 116 at one corner of the chassis 102 is displacedeither above or below the plane of the remaining road wheels 116.Additionally, the torque of the engine exerts a torsional force on thechassis 102.

The motorhome 104 of this embodiment is assembled on and around theinterconnected vehicle frame 100 and the chassis 102. The motorhome 104provides users with a vehicle having a variety of living spaces andamenities fitted within the motorhome 104. It is expected that thepartitioning of the interior living spaces and placement of interioramenities will vary depending on the needs of any particular applicationor customer.

The motorhome 104 also comprises a front loop 192 as shown in FIG. 1.The loop 192 is a generally rectangular structure attached at the frontof the motorhome 104 to the frame 100. The loop 192 provides structuralsupport for interior body assemblies in the driver's and frontpassenger's area as well as the front exterior bodywork of the motorhome104 and the front windshield. The loop 192 is assembled from a pluralityof elongate steel members via welding in a similar manner to thatpreviously described with respect to the frame 100.

The vehicle frame 100 also comprises seat supports 126. The seatsupports 126 are, in one embodiment, rectangular structures formed fromsheet steel approximately ⅛″ thick and are approximately 12 {fraction(13/16)}″ by 22 ½″. The seat supports 126 are fixedly attached to thevehicle frame 100 via a plurality of bolts and/or welding in a knownmanner adjacent the front end of the vehicle frame 100. The seatsupports 126 provide a support and attachment structure for passengerseats 128 of known types. The passenger seats 128 provide seatingaccommodations for driver and passengers in a known manner.

The HVAC system 110 in this embodiment comprises the air conditioningunit 162, the furnace 164, a manifold 166, a duct 170, at least oneregister 172, an intake 171, and a filter 173 as illustrated in FIG. 1.The intake 171 (shown in section view in FIGS. 1 and 3) commonly directsair from the interior of the motorhome 104 to the air conditioning unit162 and the furnace 164. The filter 173 is positioned within the intake171 and filters the air entering the HVAC system 110. The airconditioning unit 162 receives air from the interior of the motorhome104 via the intake and cools this filtered incoming air and directs thecool air into the interior of the motorhome 104 via the manifold 166,duct 170 and register(s) 172. The furnace 164 warms incoming air anddirects the warm air into the interior of the motorhome 104 also via themanifold 166, duct 170 and register(s) 172. The air- conditioning unit162, furnace 164, and filter 173 are commercially available and theselection of an appropriate model of air-conditioning unit 162, furnace164, and filter 173 is expected to vary depending on the size of andamount of insulation provided for a particular embodiment of motorhome104.

The manifold 166 receives air from both the air conditioning unit 162and the furnace 164 and routes the air to the duct 170. The duct 170extends substantially the length of the interior of the motorhome 104 asshown in FIGS. 1 and 3. The duct 170 carries the warm or cool air to atleast one register 172. The registers 172 direct cool or warm air,received from the duct 170, into the interior of the motorhome 104. Theregisters 172 includes a screen to inhibit objects falling into theinterior of the registers 172 and the duct 170.

The common intake 171 is advantageously formed on two sides by interiorpaneling that serves both to direct the air inside the intake 171 andalso provide interior trim in the interior of the motorhome 104. Theother two sides of the intake 171 are formed by interior surfaces of thecoach in a corner of the motorhome 104. Thus, the intake 171 issubstantially defined by body structure of the motorhome 104 thatsimultaneously serves other structural or esthetic functions therebyreducing material redundancy and effecting weight and materiel savingsfor the motorhome 104. In addition, by directing air to both theair-conditioning unit 162 and the furnace 164, the common intake 171 ofthis embodiment, obviates the need for the separate air intakes for theA/C unit and the furnace of other known designs.

The common intake 171 of this embodiment also facilitates the use of asingle filter 173 for the HVAC system 110. This single filter 173reduces the time and expense of maintaining the HVAC system 110 by theend user as compared to other designs with multiple filters for theseparate A/C and furnace systems. This commonality also reduces the timeand expense of construction of the HVAC system 110 as well as reducingthe weight thereof. In certain embodiments, the filter 173 can comprisea plurality of filter elements or stages, for example, a first filterelement/stage adapted to remove larger air borne particles and a secondfilter element/stage adapted to remove smaller airborne particles thatmay pass through the first element/stage.

The HVAC system 110, of this embodiment, is located within or below theplane of the chassis 102. Positioning the air conditioning unit 162 andthe furnace 164, which are both relatively heavy items, within or belowthe plane of the chassis 102 further lowers the center of mass of themotorhome 104 to thereby improve the road handling of the motorhome 104.The placement of the HVAC system 110 of this embodiment also distancesthe duct 170 and registers 172 from the coach roof 140. Other knownmotorhome designs rout HVAC ducting adjacent the roof of the vehiclewhich exposes the cool air to thermal heating from sunlight incident onthe roof of the vehicle. In the motorhome 104 of this embodiment, theduct 170, register 172, and air conditioning unit 162 are shaded fromincident sunlight by the motorhome 104. Thus, the HVAC system 110 canmore efficiently provide cool air to the interior of the motorhome 104.This improves the occupant's comfort in hot weather and reduces fuelcosts for powering the HVAC system 110.

A further advantage of the HVAC system 110 of this embodiment is thatthe air conditioning unit 162, duct 170, and register 172 which carrycool air are located below the living space of the motorhome 104. As iswell understood by those of ordinary skill in the art, a cooler thanambient surface, such as the air conditioning unit 162, duct 170, andregister 172 induces liquid water to condense out of the atmosphere ifthe temperature of the surface is at or below the dew point. When airconditioning ducting is routed above the living space of a motorhome,liquid water that condenses on the ducting is drawn downwards bygravity. This can induce liquid water to intrude into walls, ceilings,and other interior materials. It can be appreciated that liquid watercan readily damage the structural integrity of typical motorhomebuilding materials. Liquid water can also stain and warp interiormaterials, damaging the aesthetics of a motorhome. The air conditioningunit 162, duct 170, and registers 172 of this embodiment are positionedbelow the living space of the motorhome 104 and thus water thatcondenses out during use of the HVAC system 110 is drawn downwards andaway from the motorhome 104 without intruding into the living spaces ofthe motorhome 104.

An additional advantage of the HVAC system 110 of this embodiment isthat placement of the HVAC system 110 adjacent and below the beltline ofthe chassis 102 obviates the need to place portions of an HVAC system onthe roof of the motorhome 104. Other known HVAC systems place portionsof the system on the exterior roof of a motorhome. This requires thatthe major plane of the outer roof be lowered with respect to the roof ofthe present invention so as to maintain the overall height restrictionspreviously mentioned. Lowering the exterior roof height results incorresponding lowering of the interior ceiling height and acorresponding reduction in the interior space and livability of such amotorhome.

Yet another advantage of the HVAC system 110 of this embodiment is thatplacement of the HVAC system 110 adjacent and below the beltline of thechassis 102 distances the furnace 164 and air conditioning unit 162 fromthe interior of the motorhome 104. The air conditioning unit 162 andfurnace 164 are relatively noisy in operation. Placing, the HVAC system110 outside the interior of the motorhome 104 distances the noisesources of the air conditioning unit 162 and the furnace 164 and thusprovides a quieter, more comfortable living environment for users of themotorhome 104.

Although the preferred embodiments of the present invention have shown,described and pointed out the fundamental novel features of theinvention as applied to those embodiments, it will be understood thatvarious omissions, substitutions and changes in the form of the detailof the device illustrated may be made by those skilled in the artwithout departing from the spirit of the present invention.Consequently, the scope of the invention should not be limited to theforegoing description but is to be defined by the appended claims.

1. A heating, ventilation, and air-conditioning (HVAC) system for amotorhome having an interior living area enclosed by interconnectedcoach panels, the HVAC system comprising: a furnace unit; anair-conditioning unit wherein the furnace and the air-conditioning unitsare adapted to be positioned below the interior living area of themotorhome; a single air intake directing air from the interior livingarea to the furnace and the air-conditioning units.